From a Binary to a Quaternary Cocrystal: An Unusual Supramolecular Synthon.

Formation of a stoichiometric quaternary cocrystal consisting of resorcinol (RES), tetramethylpyrazine (TMP), phenazine (PHE) and pyrene (PYR) is described. A closed tetrameric resorcinol-heterocycle synthon, unusual in that it has two different linker bases rather than just one, is observed in this four-component solid. The tetrameric synthon is formed by two RES molecules and the two pyridine bases TMP and PHE. The stoichiometric quaternary cocrystal grows in an epitaxial fashion on the surfaces of a RES.PHE binary cocrystal which is initially obtained from the mother liquor. By indexing the common crystal faces of the binary and quaternary cocrystals, and noting that no ternary solid is obtained, a plausible mechanism has been proposed for the formation of this rare supramolecular architecture.